1. Field of the Invention
The present invention is generally related to a support system for a marine propulsion device and, more particularly, to an outboard motor with support mounts that are positioned to define an effective elastic center which is generally coincident with a torque roll axis near the center of gravity of the outboard motor while positioning the mounts away from both the exhaust system and the oil sump of the outboard motor.
2. Description of the Related Art
Those skilled in the art of outboard motor design are aware of many different types of support systems that use mounts of different shapes and configurations. Typically, the mounts are constructed of a combination of metallic structures and elastomeric elements. Some mounts are generally tubular with a cylindrical elastomeric member being disposed between a cylindrical rod and a surrounding cylindrical tube. Other mounts utilize various metallic and elastomeric portions that are shaped to suit the specific characteristics necessary for particular applications.
U.S. Pat. No. 3,599,594, which issued to Taipale on Aug. 17, 1971, describes a sound and vibration isolating mount for an outboard motor. The arrangement has a marine propulsion unit mounted rearwardly of the steering axis of an outboard motor. The mounting arrangement includes a pair of mounts secured to the propulsion unit in a vertically spaced relation approximately in alignment with the neutral or roll axis of the propulsion unit and rearwardly of or behind the driveshaft. Each mount includes a cross bar which is supported by a resilient bushing within a casing and which has ends extending outwardly from the casing transversely to the direction of motion of the propulsion unit.
U.S. Pat. No. 3,934,537, which issued to Hall on Jan. 27, 1976, describes a vibration isolating mount for an outboard motor. A propulsion unit is mounted rearwardly of the steering axis of an outboard motor. It includes a powerhead, a driveshaft housing having a driveshaft, and a lower unit carrying a propeller. The mounting arrangement includes an upper mount and a pair of lower mounts secured to the propulsion unit in vertically spaced relation and rearwardly of or behind the driveshaft. The top mount includes a cross bar which has a wedge shaped cross-section with the upper and lower surfaces thereof converging in the direction of propeller thrusts, which is supported by a resilient bushing within a casing, and which has outer ends extending from the casing transversely to the direction of propeller thrusts for connection to a swivel bracket.
U.S. Pat. No. 3,961,595, which issued to Meyer on Jun. 8, 1976, discloses a steering apparatus for small outboard motors. A steering tiller handle assembly is attached to the driveshaft housing and pivotally mounted within a swivel mounting bracket assembly. The swivel bracket assembly includes a split tubular element within which a split tubular section of the steering arm assembly is notably mounted and located encircling a tubular portion of the driveshaft housing. Upper and lower annular rubber mounts are located between the upper and lower end of the steering tubular section and the driveshaft housing. Each mount is formed with a first pair of axial slots formed in diametrically opposing sides of the mount and projecting inwardly from one end.
U.S. Pat. No. 4,979,918, which issued to Breckenfeld et al. on Dec. 25, 1990, describes an outboard motor vibration isolation system. It comprises a propulsion unit including a cavity defined in part by a wall, an opening communicating with the cavity, a rubber mount insertable into the cavity through the opening, and an expandable wedge insertable through the opening and into the cavity, securable to the propulsion unit, and engageable with the rubber mount for fixedly securing the rubber mount to the propulsion unit and between the insertable expandable wedge and the wall of the cavity.
U.S. Pat. No. 5,192,235, which issued to Dunham et al. on Mar. 9, 1993, describes an outboard motor vibration isolation system including an improved rubber mount. It comprises a propulsion unit including a wall defining a cavity, and a rubber mount which is located in the cavity and which includes an annular outer shell having an outer surface engaging the wall and an inner surface defining an axially extending bore having a minimum diameter, an inner core extending through the bore, being adapted to be connected to a kingpin, and including an end core portion having a diameter less than the minimum diameter, and an opposite end core portion having a diameter greater than the minimum diameter, and a resilient member extending between the outer shell surface and the inner core.
U.S. Pat. No. 5,443,406, which issued to Mondek et al. on Aug. 22, 1995, describes a vibration isolating mounting for an outboard motor. It comprises a propulsion unit assembly having forwardly located laterally spaced portions respectively including laterally aligned outwardly opening sockets and laterally aligned horizontally extending apertures communicating with the sockets. A kingpin assembly includes a portion located between the laterally extending portions and includes a laterally extending bore aligned with the apertures. It also includes rubber mount assemblies respectively engaged in the sockets and having respective bores in alignment with the bore in the kingpin assembly.
U.S. Pat. No. 5,881,991, which issued to Bonin on Mar. 16, 1999, describes a mount assembly for an outboard motor frame. It includes two mount assembly fittings which each have a bolt on a fitting cover and a channeled fitting plate. The mount assembly includes a threaded mounting bolt having a bolt shaft having a threaded end, an interior tubular bushing having a shaft passageway sized to receive a portion of the bolt shaft, a helically coiled compression spring of a length longer than the interior tubular bushing and sized to pass over the interior tubular bushing, and an outer bushing having a bushing passageway having a bushing passageway diameter sufficient to allow the compression spring to be positioned into the bushing passageway.
U.S. Pat. No. 6,146,220, which issued to Alby et al. on Nov. 14, 2000, discloses a pedestal mount for an outboard motor. An outboard motor is mounted to a transom of a boat with a pedestal that is attached either directly to the transom or to an intermediate plate that is, in turn, attached to the transom. A motor support platform is attached to the outboard motor, and a steering mechanism is attached to both pedestal and the motor support platform. The tilting mechanism is attached to the motor support platform and to the outboard motor.
U.S. Pat. No. 6,419,534, which issued to Helsel et al. on Jul. 16, 2002, discloses a structural support system for an outboard motor. A support system is provided for an outboard motor which uses four connectors attached to a support structure and to an engine system for isolating vibration from being transmitted to the marine vessel to which the outboard is attached. Each connector comprises an elastomeric portion for the purpose of isolating the vibration. Furthermore, the four connectors are disposed in a common plane which is generally perpendicular to a central axis of a driveshaft of the outboard motor. Although precise perpendicularity with the driveshaft axis is not required, it has been determined that if the plane extending through the connectors is within 45 degrees of perpendicularity with the driveshaft axis, improved vibration isolation can be achieved.
U.S. Pat. No. 6,645,019, which issued to Shiomi et al. on Nov. 11, 2003, describes an outboard engine system. An inertia force is generated longitudinally by a piston and is countervailed by an inertia force generated by a crankshaft. Inertial forces subsidiarily laterally generated vibrate a body of the outboard engine system laterally about a phantom center point of vibration. An elastomeric member resiliently supporting the system body on a hull has a rigidity in a tangent direction about the phantom center point of vibration which is set to be lower than a rigidity in a radial direction about the phantom center point of vibration.
U.S. Pat. No. 6,656,003, which issued to Kitsu et al. on Dec. 2, 2003, describes an anti-vibration supporting structure for an outboard engine system. A center frame is fixed to a lower end of a swivel shaft of an outboard engine system by a bolt and includes a swivel shaft extension extending downwards from the lower end of the swivel shaft and a core metal which extends laterally from a lower end of the swivel shaft extension and has a lower mount rubber integrally baked thereto.
U.S. Pat. No. 7,198,530, which issued to Rothe et al. on Apr. 3, 2007, discloses a resilient mount system for an outboard motor. The support structure for an outboard motor provides a connection bar between an engine support structure and a steering structure. A tubular outer member is spaced apart from the attachment bar and connected to the attachment bar with an elastomeric member. Vibration isolation and consistency of deformation is achieved through the interaction of the individual elements of the structure.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
A handbook, entitled “Shock and Vibration Handbook”, edited by Cyril M. Harris and Charles E. Crede, discusses the application of resilient supports on pages 3-24 through 3-29 in Volume 1 which is titled “Basic Theory and Measurements.” On these pages, the editors provide examples, equations, and discussions about various support systems in which resilient mounts are used to support a body that is subjected to vibration. Although this book does not specifically address the support mounts for an outboard motor, some of its principles are applicable to the present invention and its discussion helps to understand some of the terminology.
Certain types of outboard motors, particularly those having four stroke engines, require that portions of the exhaust system and the oil sump be located at regions within the structure of the outboard motor that can interfere with the conventional placement of support mounts. Since the positioning of support mounts for an outboard motor sometimes interfere with either the oil sump or portions of the exhaust system, it would be significantly beneficial if a support system could be provided which locates the mounts away from and in non-interfering relation with the oil sump, exhaust system, and other portions of the outboard motor.